1. Field of the Invention
The present invention relates to equipment for processing a workpiece using plasma. More particularly, the present invention relates to a system for regulating the pressure inside a process chamber of plasma processing equipment.
2. Description of the Related Art
In general, plasma processing equipment, for example, plasma etching, chemical vapor deposition (CVD), or ashing equipment comprises a process chamber in which a vacuum is maintained, a wafer chuck disposed inside the process chamber, a cover disposed at the top of the process chamber, and an exhaust unit. A wafer is loaded on the top surface of the wafer chuck. The cover includes a shower head for injecting a reaction gas into the process chamber. The exhaust unit, on the other hand, includes a throttle valve and a vacuum pump that communicate with the process chamber at the bottom thereof. The vacuum pump generates a predetermined vacuum level within the process chamber, whereas the throttle valve is opened or closed to adjust the vacuum pressure.
Recently, a pressure regulation plate has been used to control the vacuum pressure within the process chamber. The pressure regulation plate is disposed above the wafer chuck and is supported so as to be movable up and down within the process chamber. More specifically, the width of an exhaust path within the process chamber is changed by adjusting the distance between the plate and the wafer chuck, thereby in turn controlling the pressure within the process chamber.
A cam ring moves the pressure regulation plate up and down when the cam ring is rotated. Bearings are provided at the top and bottom surface of the cam ring, respectively. The bearings contact the cam ring during the rotation of the cam ring. The bearings at the top surface of the cam ring are fixed in a position. The bearings at the bottom surface of the cam ring are moved up and down in correspondence with the shape of the cam ring as the cam ring is rotated. A supporting member links the bearings at the bottom surface of the cam ring to the pressure regulation plate, whereby the pressure regulation plate moves up and down with the bearings at the bottom surface of the cam ring.
In the conventional vacuum pressure regulator of the plasma processing equipment described above, the position of the cam ring is very important in regulating the vacuum pressure. In this respect, a tool is repeatedly inserted between the cam ring and the bearings at the top surface of the cam ring to measure the distance therebetween and thereby confirm the position of the cam ring. That is, the position of the cam ring is measured manually by an operator.
However, this operation of calibrating the cam ring is troublesome. Also, a skilled operator is required to correctly measure the position of the cam ring and adjust the cam ring accordingly.